A number of components on-board an aircraft require electrical power for their activation. Many of these components are separate from the electrical components that are actually required to run the aircraft (i.e., the navigation system, fuel gauges, flight controls, and hydraulic systems). For example, aircraft also have catering equipment, heating/cooling systems, lavatories, power seats, water heaters, and other components that require power as well. Specific components that may require external power include, but are not limited to, trash compactors (in galley and/or lavatory), surface cleaning, area heaters, cabin ventilation, independent ventilation, area or spot lights (e.g., cabin lights and/or reading lights for passenger seats), water supply, water line heating to prevent freezing, charging stations for passenger electronics, electrical sockets, vacuum generators, vacuum toilet assemblies, grey water interface valves, emergency lighting, and combinations thereof.
Currently, lavatory units on aircrafts are powered by the ground power unit or the aircraft power generation system (such as the aircraft's engines or auxiliary power units (APU)). In some cases, the power generation unit requires fossil fuels, is noisy, and emits CO2. Also in some cases, such systems require more power than can be drawn from the aircraft engines' drive generators, necessitating additional power sources, such as a kerosene-burning auxiliary power unit (APU) (or by a ground power unit if the aircraft is not yet in flight). If additional power sources are used, passengers are unable to use the lavatory until the APU or ground power unit is turned on. The power consumption of the lavatory can be rather large, particularly for long flights with hundreds of passengers. Moreover, in some cases, the power must travel a long distance to reach the point of use, which can lead to power dissipation.
Moreover, operation of the lavatory requires water, so the lavatory must be connected by pipes or otherwise to the aircraft's main potable water tank. For example, coffee cannot be made, passengers cannot use the lavatories, hand-washing water is not provided, and so forth, until the APU or electrical switch is on in order to allow water to flow. Some examples of the water consumers on-board aircraft in the lavatory unit are the tap water supply and the toilet vacuum system. Aircraft typically carry large amounts of potable water in the potable water tanks, which is uploaded when the aircraft is on the ground. The lavatory unit also sometimes requires heat, which is also typically generated by separate units. For example, heated water is desirable for use in warming hand-washing water (and to prevent freezing of the water pipes), as well as the cabin heating units.
The relatively new technology of fuel cell systems combines a fuel source of compressed hydrogen with oxygen in the air to produce electrical energy as a main product. As shown in FIG. 4, a fuel cell system has several outputs in addition to electrical power, and these other outputs often are not utilized and therefore become waste. For example, thermal power (heat), water and oxygen-depleted air (ODA) are produced as by-products. These by-products are far less harmful than CO2 emissions from current aircraft power generation processes.